An image forming process of an image forming apparatus is interrupted when a power failure occurs or when amain body cover is opened. Since deviation in the timing of each function within the image forming apparatus is generated when the image forming apparatus returns from the interruption, defects are generated. For example, unnecessary toner may adhere to a charged photoconductor, and in turn stain a transfer roller. The interruption corresponding to the power failure or the opening of the main body cover is generated at an unexpected timing, and so it is difficult to take measures that would prevent the occurrence of defects.